Coil winding



July 10, 1928.

I. H. SUMMERS Fiied Dec. 29, 1925 Inventor: lvan H Summers .JT HsAt-torneg Patented July 10, 1928.

UNITE-D STATES IVAN H. SUMMEBS,- OF- LYNN, MASSACHUSETTS,-:ASSIGNOR TOGENERAL COMPANY, A CORPORATIONQF NEW YORK.-

1,677,007 jPAT'ENT JGFFICE.

ELECTRIC I i don. ,WINDIING. 4

I I Application filed December y et e freletestonc l Wiridings '33.?rfio r'e partieularly to the windings of alter-'- nating eurrentdynamo-electric machinesi In large alternating current generators in 5whichthe windings, which are disposed in the armature slotsfconsist' ofcoils formed of conductors *ofcon's i'derable' depth, the magneticflux'across the slots, due tothe'current'in the conductors; gives ri se toparasitic 'voltages'within the condu etorsl'ivhich induce eddy currentstherein. These currents if of sutficient magnitude may pro'duce'objectionable heating of the winding. and cause the material of'theconducto'r'to be inefficiently utilized." 'L In siioh "a machine, where,each armature slot i's 'filled'i'vith severa'l'condiictors each of whichis'made of insulated strands, andarranged o'ne'above the'other,'the fluxdue to ff 'c'u'i'renticatrriedr by the bottom jconductor. has

a path partly'through 'th'e' iidn 'coreand partly'through thespace'between'the sidelwalls of the slot. "'The. distribiiti'ri n Qfthlis' "fluxffor -conven' iencemay be regarded as" uniform 'frolntheto'p of; the conductor 'to th'e mouth of the slot. 7 Likewise,thelfiujt ldue to curi ent carriedhy the" second conductor from; the-bottom also maybe regarded Q'as 'evenlydistributed in the space betweenthe slot walls from 'the'top of that conductor to'the mouth of'theslot-and similarly for the remaining :condu'ctors in the slot. The total'fiux'density in the slotytherefore, is not uniforrn, but increases fromthe top' of the bottom conductor to the mouth of the slot. In the above,consideration has been given only to the flux between the top of aconductor and the mouth of the slot." The c iii' r e'n't in each con}ductor produces a flux throughout the depth of the conductor whicli fiuxincreases @from the bottom of-the top of the'conduc tor and produces avoltagein the conductor which increases from the bottom of theconductorto the top thereof in approximately a parabolic inannerf Thetotalvoltage in any half turn ofa. coil is thus made up of avoltage duetn'the flux-of that half t'u r'ii'of the coil plus-the voltage due tothe flux from the other'half turns of the coil below the one inquestion.This voltage va'iiesin magnitude for each half turn, being greatest forthat'hal'fturn at the top of: the slot. The parasitic or difference nvoltage between strands, induced in the twolsides of a ma chinewound-coil are opposedto'each other 'du eltol thefact thatfthe reversingend turn oftlie"winding'finverts' one side of thecoil relative to thefotlier'SiHeT As 'a result of .thisreversal, the difference ofthevoltages 'inducedinthelbp an'd'the bottorn'portions (so of aemanati-info 'eid ofithe coil is partly.neutralizedby that'infliefdth'er side of the 'coiL But, lieca\i'see f th'iinequ'aldistiibhtioil ""ofjfiux throughout the depth of the-$1 6555'poin deut'eb there still 5- "xiiain's a voltage" difl e'reiice b" tween the top andthe 'bo'ttx'ii'ii fpoi tio'ifs' of the c'ofidu'c'tor whioh'givesirise'to objectioha'ble eddycur:- -i'ents 4 th'rougb'f'thenductdr'' farming" the winding; The parabolic distribution of"voltage-in the half-turns"pf a' coi'l referred mm be 'resolved' in-toelementary p'arabo'li corfiponent and a lih'ealfi component 'yhavm aslope ofan order cmrespontlingto the her of conductors in the slot belowthe one in question." Thearrain'g'enienfi of strands in accordancewith-in invention flees} notplirport to 'co'm'pletely alan'oe the-parabolieeli -ments,-'-sinee', -even'wheifi th'o'se' ofbp'p'o'site sosense are-balanced, a sniall remdinihg un equal vdltagefli'stribiitioiiwill I em'airi. "It; is possible, however; to balance the linear-"ele-mnts-sde6mpltelythat the reinainin" eddy current lossesewillzbeiredueed'to a neg igible amount. 'Anvolijectjof my invention, therefore,'isthe provision of 'animproved' multi turn winding im which theeddy -current losses in rthe stranded conductors thereof are reduced! to arelatively low value;

In connection with the above explanation, reference ;is made to. the;article entitled, Eddy, currents-in stator windings by H. \V. Taylor infiThe Journal of the Instituti01roElectrical Engineers- (London) forAPri1.1920,.-v01. 58.

Myinvention-will be better understood from the following descriptiontaken in-connection .with! l the accompanying drawing, and itsscope willbe pointed out in-the ap- 10o pended claims. 1' 4 ,In the accompanyingdrawing, Fig.1 representsia.two turn stranded coil according to 1nyinvention;. Fig, 2 is across section-on line 22 of,Fig.' l, sh0wing-thesides of the coil in their respective armature slots; and Eigs. 3 8nd .4are representations, showing an arrangement for a three-turmcoil, 'correspondin respeetivelypwith Figs. 1 and 2 for the two-turn coil.

In Fig. 1J1 have illustrated a two-turn form-wound coil 1 which has ateach end thereof the usual reversing end turns Z. In order toiforin'thecompletc armature winding a plurality of such coils areconnected together in the usual manner, which is 'ell known in the art.The conductor 3. of which the coil is formed, comprises four doublestrands forming four layers or laminations, the strands being madedouble to bette'rifacili tate'the edgewise' bending theref.. The:strands are separately insulated throughout t heir length; except, ofcourse, ati';the ,teriiiinal s l and 5 where suitable solid connectionsare inade with adjacent coils, the se yeifal strands of the;coii ductorof each coil iorniiii gl so inany separate parallel circuits i flniaqtwoturn c0il, as;sliown for ex- :ample by. Fig.1 I give the conductora tw st, .6, of l 80,.f. in eacli turn of the coil at the rear endorend,-opposite.the connection end of coil. 'l he eflectof this 180 twistwill .be more clearly seen-by referring to Fig. 2. Here the two sides ofthe coil are shown in ,their respective slots Tand S, which are spacedapart in thearn' ature either a full pole pitch or approximately so,according to whethertht: winding has a full or a fractional-pitch -Herefor/convenience in fol lowing the;re versals of the conductor due to,tliei.end, tl li'ns 2 ;and the twists (i I have s l l oyvnt-he'conductor having one double strandshaded. {The-slots 7 and 8 arefour conductors deep, the four. conductor positionsf in the-=slQti:beingdesignated as -positiioms li|2fl3l and 4M ii'Ii-lioitdtal--voltage-inducedt-iin'la-nyi part-ieulan strand-of .the' con-'dL-QtQl'tldliQutOt the currentii'iiall -the other strands is atpat'abolicifui'ie'tion of the-height oft-the strandvini the slots-Howev'er. the-differencd i intl euroltages[induced in' a in twostiia-nds, -,ditfiei-i-rig inuheight "by -a definite numberOf=StU2lll1dS5 l allinear function of the average heighb of 'the two=strandsconsidered. .'.[hus;iiwl ile 'thelvoltagedistribution across theStrand-inmnygfifiiveh conductor isnot ex- :idtly-llineam tihedifferences inj'voltage lietweeni tlielltlop alrd'tlie bott t tliistrands of the 'oohduetiorisla"-lineai'.1fii'netion 'of the position ofthe conductor in *t-lie-lslotfiTlie deviation 'nf" tlie "t*oltzigeRisa-mutto frorii a straight lihe function 1% very-515ml];a in-b-,viously statedyandain tli ef following discus si0n"-'he' arnsiti o'r 1Voltage difference a between the strands of the condi'ietor willilieconsidered -to "be"-'-ii* linear 'ftlllt'titiii til the 'height of-the"cdndutft'oi' in' 't lie' slot.'I Tlie linear" component of the"parasitic" 'rbltii-igta ttecting the'dtrantle'd 'con'diit-ir'iiiposition 1;; be'ing' at the'bot'toln 6r the' id't. will 1 taken'as0;andfsint 'eie'ael conductor fe'eted by'tiieffiqx'o'f eh'edfidti tdrjblow it. as explained above," 't lie loi'resiio iifiii g voltages of theC(HHlllC'ftifR l t l i ositio ns nated;an

les

of the slotto its iiiouth,,a s alreadyeaplai ned,

the reversal of the conductor diie;to1itsjp z issiiig around theusualreversing end turn is not alone sufiicient to equalize, in th'e jtwosides of the coil ;the i'roltage difi'erence produced in. thetopla-ndgthe' bottomstraiids oif the conductor. I thereforegine, thecondlictor the 180 twist, :6, in each Referring to EigLQ qwe shall. callthe direction of the parasitic voltageinducedbin the shaded andother,strands;.of,:the-,-eonductor; positive, when thegslmded strandisat the top, and when the shaded portion is.fat the bottom of thecoiidiictorg we.shall eall the direction of this parasitic ordifference-in voltage negative. Starting witltg-the coniluctor iiithe-bgttom islot fland adding: up the difference in -\'ol tagesinducediin thei top and bottom strands of the half turns-0fa single coilWe have plus 0, plus l ,-,Ii iinu s; l, and minus 2 which equals 0. Itwill; thus; be seen that by my arrangement l have' elii'ni tendencytowardeirculating'currents in t e coilQduto the lineaizeomponents ofinduced parasitic Vo lt a'ge and ithatwthe Wil s; h jeiw'eamar beaso iilr' q t trixir thwnut e W m v i g eewf. ,sia e wei w giei dire mieddy@1934 l stran i a nweulatedaan ifl wi ranclseo np g si ig the non etortii re -solidly 2 jnlnll s l which equals; gplus.nli wInnthis ease theresultant has not been reduced to t) but the value has been so farreduced that it has little etfect. lVithout the twist- I have put in thecoil, this resultant would have been 9, so that by my insertion I havereduced the linear voltage to 1/9, and the losses therefore to 1/81, inthis case. For coils having a greater number of turns, a similararrangement may me made use of, wherein the conductor is twisted one ormore times in its several turns at the ends of the coil. In case it isnet thought best to seek perfect immunity from eddy currents, but merelyto reduce them by a large percentage, I prefer to place but a singletwist in one coil turn at the connection end of a multiturn coil asillustrated in Fig. 3. It is evident from a study of the usual form coilwinding that the most convenient place to make this twist is at thispoint, for by placing it there only one turn need be unwound, twistedand rewound; and furthermore, the twist is in the top of the coil, whereit will least interfere with the binding bands that resist short circuitstresses. The reduction by this single twist is not great enough to besatisfactory in two turn coils, and so in this case, at least, it isdesirable to introduce two twists as shown in Fig. 1. For six-, sevenandeight-turn coils, the percentage of reduction of losses is not verygreat, but in those cases the circulating current loss is so small, dueto the relatively large number of turns in the coil, that it is notnecessary in these cases to obtain any greater reduction.

With the twist only in the top conductor on the connection end of thecoil, the circulating current loss, due to the linear parasitic orvoltage difference between the strands in coils with different numbersof turns, will be reduced in the following proportions:

In cases where the space available on the connection end is limited, itmay be preferable to place the twist at the back end of the coil at. theend of the bottom conductor on the top coil side. This position of Inthe figures of. the drawing the conductor terminals 4 and 14 are shownin the bottoms of the slots. Evidently, it Will be equally possible tohave them enter the tops of the slots. This is not ordinarily done,however, as it brings the terminals to the air gap side of the windingwhere the available space is very limited, unless the coil is fanned outat a considerable angle. However, where this fanning out is notobjectionable, this conductor may be placed in the top of the slot, andconsequently, the desired point of twist will then be transferred to theback end of the coil at the end of the first half turn, instead of beingon the connection end, a whole turn distant from the terminal.

\Vhat I claim as new and desire to secure Y by Letters Patent of theUnited States, is

1. A innlti-t-urn coil having reversing end turns and comprising aconductor formed of a plurality of insulated strands, the conductorhaving a twist of 180 in one of the end turns of the coil.

An armature coil having reversing end turns and comprising a pluralityof turns of a. conductor formed of insulated strands, the conductorbeing twisted in one of the end turns of the coil to maintain the orderof the strands in the two sides of that turn of the coil unreversed.

3. A multi-turn coil for a dynamo-electric machine having reversing endturns and comprising a conductor formed of a plurality of insulatedstrands, the conductor of the coil having a twist of substantially 180in the upper turn at one end of the coil.

4. A form wound armature coil having reversing end turns and comprisinga. plurality of turns of conductor formed of separate insulated strands,the conductor being twisted in an end turn at the connection end of thecoil to maintain unreversed the order of the strands of the conductor inpassing around said end turn.

5. A form wound armature coil comprising a plurality of turns of aconductor formed of insulated strands, the upper turn of the coil at itsconnection end having a twist of substantially 180.

In witness whereof, I have hereunto set my hand this 10th day ofDecember, 1925.

